Source: USGS

Effective April 2, 2007, updates to the radiometric calibration of Landsat 5 (L5) Thematic Mapper (TM) data processed and distributed by the U.S. Geological Survey (USGS) Center for Earth Resources Observation and Science (EROS) will be available. The full implementation of these processing changes will lead to an improved Landsat 5 TM data product that will be more comparable to Landsat 7 Enhanced Thematic Mapper Plus (ETM+) radiometry, and will provide the basis for continued long-term studies of the Earth’s land surfaces.

Although this calibration update applies to all archived and future L5 TM data, the principal improvements in the calibration are for data acquired during the first eight years of the mission (1984-1991), where the change in the instrument gain values is as much as 15 percent. Additionally, the radiometric scaling coefficients for Bands 1 and 2 have also been changed for approximately the first eight years of the mission. Users will need to apply these new coefficients to convert the calibrated data product digital numbers to radiance. The scaling coefficients for the other bands have not changed.
The lifetime gain model that was implemented on May 5, 2003 for the reflective bands (1-5, 7) will be replaced by a new lifetime radiometric calibration curve derived from the instrument’s response to pseudo-invariant desert sites and from cross-calibration with Landsat 7 ETM+. Along with the revised reflective band radiometric calibration, an instrument offset correction of 0.092 W/ (m2 sr µm) or about 0.68 K (at 300 K) will also be added to all L5 TM thermal band (Band 6) data acquired since April 1999. For detailed information and background on the reasons for this change, see the Revised Landsat 5 Thematic Mapper Radiometric Calibration (2007).